Means for minimizing distorting of duplicating masters in use



March 15, 1955 B. E. ANDERSON ETAL 2,704,025

MEANS FOR MINIMIZING DISTORTION OF DUPLICATING MASTERS IN USE 2 Sheets-Sheet l Filed Jan. 24, 1952 INVENTORS.'

ATTRNEYS.

March 15, 1955 B. E. ANDERSON ET Ax. 2,704,025

MEANS FOR MINIMIZING DISTORTION OF DUPLICATING MASTERS IN USE 2 Sheets-Sheet 2 Filed Jan. 24, 1952 INVENTORS.'

BY @wm ATTURNEYS.

United States Patent O MEANS FOR MINIMIZING DISTORTION OF DUPLICATING MASTERS IN USE Bror E. Anderson, Park Ridge, Angelo H. Caliendo, Cicero, and Henry E. Renwick, Wheaton, Ill., assignors to A. B. Dick Company, Niles, Ill., a corporation of Illinois Application January 24, 1952, Serial No. 263,112

4 Claims. (Cl. 101-128.1)

This invention relates to duplicating machines and it relates more particularly to means for mounting a duplicating master, such as a stencil sheet, lithographie plate or hectograph master in a manner to minimize stretch and distortion as an incidence to normal use.

In the use of high speed rotary machines for printing by direct or offset method, the duplicating master is clamped at its leading edge or both leading and trailing edges for mounting about the periphery of a rotatable cylinder. The impression roller or cylinder pressure tends to cause the master to stretch or distort in use.

.Such stretch or distortion has been found to occur in excessive amounts where the master is formed of fibrous material and when substances applied onto the surfaces thereof are capable of absorption into the fibrous base with a resultant weakening of the integrity thereof. Such possible changes in the dimensions of the duplicating master in use causes distortion of the printing image and lack of registration of the image on the impression paper.

Conditions of this character exist in the use of a paper base lithographie plate wherein the plate surface is constantly wet in operation with an aqueous repellent medium for non-imaged portions of the plate while oil base inks or the like are applied to the image formed thereon. Similarly, the surface of a hectograph spirit master is also wet with aqueous medium which may be applied to the copy sheet onto which the impressions are transferred upon contact or else applied directly to the master for transfer.

For the present, consideration will be given more specifically to problems of equivalent character existing in stencil duplication wherein the stencil sheet is mounted on the periphery of an inking cylinder having an ink distributing pad positioned therebetween. Forces causing stretch and distortion of the stencil sheet exist in normal operation with oil base inks but the problem becomes aggravated with the more recent use of water base stencil duplicating inks for copy work.

Generally, stencil sheets are cut to lengths corresponding to the greatest dimension of copy produced therefrom, such for example as legal size copy of about 15 inches. The inking cylinder of the duplicating machine is also dimensioned to correspond therewith. When legal size copy is to be reproduced, the entire usable area of the stencil sheet is operative and remains substantially in surface contact with the ink pad. It has been found that the ink pad provides some anchorage for the stencil sheet and thereby minimizes the effects operative to cause stretch or distortion of the stencil sheet in use.

Most of the tension tending to break or distort the stencil comes from the trailing end portion of the legal size stencil where the impression roller rides directly on the stencil when letter size copy is being run. Thus, when copy of less than full legal size is to be duplicated, it is necessary to cover unused portions of the ink pad with what is generally referred to as a block-out. The block-out has in the past released the tail portion of the stencil from contact with the ink pad with the result that forces become operative in use to cause stretch or elongation of the stencil especially when the integrity of the stencil sheet is reduced by the presence of high moisture.

An object of this invention is to provide means for mounting a duplicating master of the type described in a manner which minimizes stretch and distortion thereof 1n use.

Another object is to provide means for reducing stencil stretch and it is a related object to provide block-out 2,704,025 Patented Mar. 15, 1955 means in stencil duplication which minimizes slippage of the stencil sheet to reduce stretch thereof in use.

These and other objects and advantages of this invention will hereinafter appear and for purposes of illustration, but not of limitation, embodiments of the invention are shown in the accompanying drawings in Which- Figure l is a sectional elevational view showing a portion of the inking cylinder of a stencil duplicating machine with the tail portion of the stencil sheet blocked out for reducing the duplicating area thereof;

Figure 2 is an enlarged sectional view taken of the portion of the assembly shown in Figure l;

Figure 3 is a perspective view with parts broken away more clearly to illustrate the assembly shown in Figure 1 for mounting a stencil sheet on the inking cylinder;

Figure 4 is a sectional elevational view of an assembly embodying features of this invention for mounting a master such as a lithograph or hectograph master on the periphery of a rotating duplicating cylinder;

Figure 5 is an enlarged sectional view taken of a portion of the assembly shown in Figure 4;

Figure 6 is a perspective view with parts broken away more clearly to illustrate the assembly shown in Figure 4',

Figure 7 is a fragmentary perspective View of a modification of an interlayer embodying features of this invention, and

Figure 8 is a perspective view in section of a modification embodying features of this invention.

It has been found in accordance with the practice of this invention that stretch which has heretofore occurred in a stencil sheet 10 having a portion 11 thereof blocked out from contact with the ink pad 12 on an inking cyl inder 13 may be largely overcome when the block-out sheet 14 is provided with a non-skid surface 15 to establish a more desirable gripping relation with the tail end of the stencil sheet in operation. Although the block-out plate embodying features of this invention may be embodied as an integral part of the ink pad to reduce the effective length thereof without introducing raised portions, very often use is made thereof as an interlayer between the underside of the duplicating master and the cylinder or ink pad surface.

The desired characteristics have been found to exist in a block-out sheet 14 having surface roughness such as may be provided by relatively sharp grits 16 anchored onto the surface of the block-out sheet by a water resistant exible resinous material 17, such as a cured ureaformaldehyde resin, phenol-formaldehyde resin, melamine-formaldehyde resin, alkyd resin or polyester resin, or by a plasticized or unplasticized thermoplastic or rubber-like material such as polystyrene, polydichlorosty rene, polyethylene, polybutylene, polyalkyl acrylate resin, polyvinyl choride, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, rubber hydrochloride, chlorinated rubber or the like or mixtures thereof, or a flexible water insoluble natural resin such as shellac, coumarone indene and the like.

The grits dispersed over the surface of the block-out plate should be of a size capable of extending from the surface of the plate for embossment into the underside of the coated stencil sheet but the grits should not be so large as to penetrate through the coated sheet. For example, number -220 grit has been found to provide a desirable surface when bonded onto a block-out sheet with a cured alkyd resin (polyhydric alcohol-polybasic acid condensation product). In practice, it is preferred to make use of a block-out sheet of the type described having no surface roughness on the leading edge so as to provide a more desirable relation in combination with the assembly described.

Instead of a grit surface, roughness of the desired character to provide the improved gripping relation with the blocked out portion of the stencil sheet may be secured by a low thread count fabric 30 coated on one side 31 to impart ink impermeability while maintaining flexibility but with the threads exposed at the opposite side to permit embossment in the underside of the stencil sheet in contact therewith to reduce slippage and stretch in use. For example, a low thread count 44 x 36 gauze coated with polyvinyl acetate and fabricated by the Susquehanna Mills for wall covering may be used.

The desired gripping relation to resist slippage and distortion may be achieved also by the use of an interlayer in the form of a plastic tilm, resinous coated sheeting or the like embossed to provide raised points or lines 41 preferably arranged parallel to the tail clamp to extend crosswise of the sheet and minimize endwise distortion or stretch. Effect similar to that of the embossed sheet results from creeping to provide wrinkles in the surface of the sheet preferably parallel to the tail clamp. Embossures to provide unevenness in the surface may also be designed to provide valleys which function as suction cups to anchor the plate in position of use on the cylinder.

By way of further modification, stencil stretch may be reduced by the use of a tape, sheet or the like which has a pressure-sensitive adhesive on both sides to establish the desired gripping relation between the tail of the stencil sheet and the block-out. Such pressure-sensitive material should have high wet strength, good ilexibility and be capable of maintaining a bonding relation under conditions of use such as in the presence of water and oils existing in high proportion in Water base stencil duplicating inks and oil base stencil duplicating inks respectively.

The problem faced in the mounting of lithograph and hectograph masters is substantially similar to that which exists in the area of a blocked out stencil sheet except that an ink pad is not positioned between the plate and the mounting cylinder to impart some degree of anchorage. In lithograph or hectograph printing, the leading edge 20 of the plate 21 is clamped to the supporting rotating cylinder 22 and the body portion of the plate merely rests upon the cylinder surface which, in the past, has embodied no means to establish a gripping relation or anchorage of the type to prevent slippage or stretch.

In accordance with the practice of this invention, a flexible, high wet strength sheet 23 embodying the characteristics of the block-out sheet previously described is provided about the periphery of the duplicating cylinder 22 with the portion 24 having a non-skid surface uppermost to engage the underside of the plate when mounted thereon. The interlayer sheet or block-out sheet is characterized by insensitivity to moisture so as to resist stretch or deformation in use and the surface 24 of the interlayer becomes embedded in the underside of the plate to establish a desirable gripping relation therewith to prevent slippage and deformation in use.

As in the block-out sheet previously described, an interlayer in the form of a tape having pressure-sensitive adhesive on both sides may be used to establish the desired anchoring relation.

en the interlayer or block-out sheet is used in accordance with the practice of this invention further improvement will result in the use of a stencil sheet, hectograph master or lithograph master by having a slightly impressionable coating on the underside which permits the surface roughness of the interlayer to become embedded therein or, in the alternative, the backside of the duplicating master may itself be formed with surface roughness to become interlocked with the surface of the interlayer for complete integration therewith in position of use.

It has been found that the use of interlayers which are unaiected by the liquids used in duplicating work and incapable of distortion by impression roller pressure or the like and which embody surface roughness of the type described to provide a better gripping relation with the underside of the duplicating master in use markedly reduces stretch heretofore responsible for image distortion and improves registration when running copy on preprinted forms or the like.

It will be understood that numerous changes may be made in the details of construction, arrangement and operation without departing from the spirit of the invention, especially as defined in the following claims.

We claim:

1. In a rotary duplicating machine, the combination of a duplicating master formed of materials which permit the master to slip and stretch under conditions of use, a cylinder mounted for rotational movement in the machine, means for securing the leading edge of the master to the cylinder so as to dispose the master on the peripheral surface thereof in position of use, and a member between the cylinder and master having a surface adjacent the underside of the master with elements projecting from the surface for embedding into the underside of the master to establish a gripping relation therewith in use for minimizing stretch and slippage.

2. In a irotary duplicating machine as claimed in claim 1 in which the elements projecting from the surface of the member between the cylinder and the master comprise the threads of a flexible open weave fabric coated on the opposite side whereby the thread pattern is exposed on the side adapted to be positioned adjacent the underside of the master for establishing a gripping relation therewith in use to minimize slippage and stretch.

3. In a rotary duplicating machine as claimed in claim l in which the duplicating master is a stencil sheet.

4. In a rotary duplicating machine, the combination of a duplicating master formed of materials which permit the master to slip and stretch under conditions of use, a cylinder mounted for rotational movement in the machine, means for securing the leading edge of the master to the cylinder so as to dispose the master on the peripheral surface thereof in position of use, and a member positioned between the cylinder and master formed of a exible fabric having particles of grits embedded into the surface thereof adapted to be positioned adjacent the underside of the master for establishing a gripping lrnelation therewith in use to minimize slippage and stretc References Cited in the file of this patent UNITED STATES PATENTS 253,196 Flagg et al. Feb. 7, 1882 881,307 Dick Mar. l0, 1908 881,448 Smith Mar. 10, 1908 1,009,709 Furber Nov. 21, 1911 2,246,795 Daniels June 24, 1941 2,413,664 Toland Dec. 31, 1946 2,556,144 Newman June 5, 1951 FOREIGN PATENTS 529,809 Great Britain Nov. 28, 1940 551,180 Great BritainV Feb. 11, 1943 

